Field of the Invention
This description relates generally to ophthalmic lenses used in eyewear that provide near vision as well as distance vision correction.
Description of the Related Art
Refractive errors are the most frequent eye problems encountered by patients of all ages. Refractive errors include (i) myopia or near-sightedness, a condition in which objects at a far distance (e.g., at a distance greater than 20 feet) appear blurred; (ii) hyperopia or farsightedness in which in which objects at a near distance (e.g., at a distance less than 2 feet) appear blurred; (iii) astigmatism in which objects at near distance, far distance as well as intermediate distance appear blurred; and (iv) presbyopia that includes loss of the ability of the eye to focus on near objects. These and other refractive errors can be corrected, for example, by ophthalmic lenses such as those used in eyeglasses.
Patients suffering from hyperopia that also suffer from presbyopia or may require a first pair of ophthalmic lenses that provide distance vision and a second pair of ophthalmic lenses that provide near vision. Bifocal lenses can correct both near and far vision with the same lens and eliminate the need for separate pairs of ophthalmic lenses for viewing objects at near and far distances. Presbyopic patients can also benefit from progressive lenses that can correct near, intermediate and far vision.